Flexible panel and method of fabricating the same

ABSTRACT

The invention provides a flexible panel and a method of fabricating the same. The flexible panel includes a flexible substrate, an overcoat layer and a device layer. The overcoat layer is disposed over and directly contacting the flexible substrate. The device layer is disposed over the overcoat layer. In the invention, the flexible substrate can be directly formed on the carrier, such that an additional layer that helps release between the carrier and the flexible substrate may not be needed, and the flexible substrate can be separated from the carrier by the overcoat layer thereon, thereby reducing the production costs and ensure the quality of the flexible panel.

RELATED APPLICATIONS

This application claims priority to Chinese Application Serial Number 202010601029.0 filed Jun. 29, 2020, which is herein incorporated by reference.

BACKGROUND Field of Invention

The invention is related to a flexible panel and a method of fabricating the flexible panel.

Description of Related Art

With the progress of panel production technology, bendable flexible panels, including flexible display panels, flexible touch panels, flexible touch display panels, and so on, can be fabricated. However, for the production of conventional flexible panels, an additional layer, such as a sacrificial layer, a release layer, or a release layer with an adhesive layer, is usually formed between a carrier and a flexible substrate, so as to separate the flexible substrate from the carrier in a subsequent process, thus leading to an increase of production cost. On the other hand, if the adhesive layer contains volatile materials, the quality of the flexible panel would be affected.

SUMMARY

The purpose of the invention is to provide a flexible panel and a method of fabricating the same, in which a flexible substrate can be directly formed on a carrier, such that an additional layer that helps release between the carrier and the flexible substrate may not be needed, and the flexible substrate can be separated from the carrier by an overcoat layer thereon, thereby reducing the production costs and ensure the quality of the flexible panel.

One aspect of the invention is directed to a flexible panel which includes a flexible substrate, an overcoat layer and a device layer. The overcoat layer is disposed over and directly contacting the flexible substrate. The device layer is disposed over the overcoat layer.

In one embodiment of the invention, the device layer comprises one of a touch electrode layer, a liquid crystal display structure, an organic light emitting diode display structure and a micro light emitting diode display structure.

In one embodiment of the invention, a thickness of the overcoat layer is in a range from 0.5 microns to 2 microns.

In one embodiment of the invention, the flexible panel further includes an optical layer disposed between the overcoat layer and the device layer.

In one embodiment of the invention, the flexible panel further includes a waterproof layer disposed between the overcoat layer and the device layer.

Another aspect of the invention is directed to a method of fabricating a flexible panel which includes the following steps: providing a carrier; forming a flexible substrate over and directly contacting the carrier; forming an overcoat layer over and directly contacting the flexible substrate and the carrier; forming a device layer over the overcoat layer; performing a cutting process on a stacked structure of the flexible substrate and the overcoat layer; and separating the device layer, the cut flexible substrate and the cut overcoat layer from the carrier.

In one embodiment of the invention, a peeling force between the overcoat layer and the carrier is greater than a peeling force between the flexible substrate and the carrier.

In one embodiment of the invention, a peeling force between the overcoat layer and the carrier is greater than or equal to 100 gf/cm.

In one embodiment of the invention, a peeling force between the flexible substrate and the carrier is less than or equal to 20 gf/cm.

In one embodiment of the invention, water contact angles of the flexible substrate and the carrier are all greater than 40 degrees.

In one embodiment of the invention, an adhesive force of the overcoat layer obtained according to an ASTM D3359 cross-cut test is greater than 4B.

In one embodiment of the invention, the overcoat layer includes an organic material layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows.

FIGS. 1A-1D are structural diagrams of respective flexible panels in accordance with various embodiments of the invention.

FIGS. 2A-2E are schematic cross sectional views of intermediate stages illustrating a method of fabricating a flexible panel in accordance with some embodiments of the invention.

DETAILED DESCRIPTION

Specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, however, the embodiments described are not intended to limit the present invention and it is not intended for the description of operation to limit the order of implementation.

It will be understood that, although the terms “first,” “second,” and “third” may be used herein to describe various elements, components, areas and/or portions, these elements, components, areas and/or portions, should not be limited by these terms. These terms are only used to distinguish elements, components, areas and/or portions.

Terms used herein are only used to describe the specific embodiments, which are not used to limit the claims appended herewith. Unless limited otherwise, the term “a,” “an,” “one” or “the” of the single form may also represent the plural form. In addition, the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Regarding the term “coupled” used in the following description, it may be used to indicate that two or more elements are in direct physical or electrical contact with each other, or may also mean that two or more elements may not be in direct contact with each other. “Coupled” may still be used to indicate that two or more elements cooperate or interact with each other.

In the disclosure, a touch electrode layer may be used for touch detection, and it may be a single-layer electrode structure, such as a single indium tin oxide (SITO) structure, a single-layer multiple-touch structure, or a double-layer electrode structure, such as a double indium tin oxide (DITO) structure. The material of the touch electrode layer is not limited to indium tin oxide (ITO), which may also be metal such as gold and silver, or may be, for example, indium zinc oxide (IZO), indium oxide, tin oxide or another suitable conductive material. A liquid crystal display panel may be of various types, such as twisted nematic (TN), electrically controlled birefringence (ECB), in-plane switching (IPS), fringe-field switching (FFS), vertical alignment (VA) or non-aligned polymer-dispersed liquid crystal (PDLC), or may be an organic light-emitting diode (OLED) display panel, a mini-LED display panel or a micro-LED display panel.

FIG. 1A is a structural diagram of a flexible panel 100A in accordance with some embodiments of the invention. As shown in FIG. 1A, the flexible panel 100A includes a flexible substrate 102, an overcoat layer 104 and a device layer 106. The flexible substrate 102 is bendable, and the thickness thereof may be less than 20 microns, e.g. 8 microns to 10 microns. In addition, the flexible substrate 102 may be formed of a transparent material. In some embodiments, the material of the flexible substrate 102 may include polyimide (PI) and/or another suitable material. The overcoat layer 104 is disposed over the flexible substrate 102, and the material of the overcoat layer 104 may include acrylic, diethylene glycol methylethyl ether, methyl 3-methoxypropionate, poly-functional monomers (e.g. ethylene glycol dimethacrylate and/or the material of CAS No. 478556-66-0), additives (e.g. the material of CAS No. 14513-34-9). The thickness of the overcoat layer 104 may be less than 2 microns, e.g. about 0.8 microns to 1.2 microns. The device layer 106 is disposed over the overcoat layer 104. According to the type of the flexible panel 100A, the device layer 106 may be a touch electrode layer, a liquid crystal display (LCD) structure, an organic light emitting diode (OLED) display structure or a micro light emitting diode (micro LED) display structure, but is not limited thereto. For example, if the flexible panel 100A is used for touch detection, the device layer 106 may be a touch electrode layer; and if the flexible panel 100A is used for image display, the device layer 106 may be an LCD structure or an OLED display structure. Furthermore, in some embodiments, if the flexible panel 100A is a touch panel, then the flexible panel 100A may be bonded to an additional display panel to form a touch display panel.

FIG. 1B is a structural diagram of a flexible panel 100B in accordance with some other embodiments of the invention. In comparison with the flexible panel 100A shown in FIG. 1A, as shown in FIG. 1B, the flexible panel 100B further includes a waterproof layer 108 disposed between the overcoat layer 104 and the device layer 106, so as to further block external moisture from entering into the device layer 106 and corroding the electronic components of the device layer 106. The waterproof layer 108 may include aluminum oxide, aluminum nitride, silicon oxide, silicon nitride, combinations thereof and/or another suitable waterproof material. In addition, the waterproof layer 108 may be formed of a single-layer structure or a multi-layer structure.

FIG. 1C is a structural diagram of a flexible panel 100C in accordance with some other embodiments of the invention. In comparison with the flexible panel 100A shown in FIG. 1A, as shown in FIG. 1C, the flexible panel 100C further includes an optical layer 110 disposed between the overcoat layer 104 and the device layer 106, so as to adjust the color presented by the flexible panel 100C. For example, if a particular material is selected to form the overcoat layer 104 so that the color presented by the whole flexible panel 100C turns yellowish, the optical layer 110 may reduce the degree of yellowish, in order to meet the taste requirements of some customers or users. The optical layer 110 may include niobium oxide (e.g. Nb₂O₅), silicon oxide, titanium oxide, silicon nitride, magnesium fluoride, combinations thereof and/or another suitable material. In addition, the optical layer 110 may be formed of a single-layer structure or a multi-layer structure.

FIG. 1D is a structural diagram of a flexible panel 100D in accordance with some other embodiments of the invention. In comparison with the flexible panel 100A shown in FIG. 1A, as shown in FIG. 1D, the flexible panel 100D further includes a waterproof layer 108 and an optical layer 110, in which the waterproof layer 108 is disposed between the overcoat layer 104 and the optical layer 110, and the optical layer 110 is disposed between the waterproof layer 108 and the device layer 106, so as to adjust the color presented by the whole flexible panel 100A. The waterproof layer 108 and the optical layer 110 of the flexible panel 100D may be respectively the same as the waterproof layer 108 of the flexible panel 1006 and the optical layer 110 of the flexible panel 100C. Further, the positions of the waterproof layer 108 and the optical layer 110 may be exchanged, i.e., the optical layer 110 may be disposed between the overcoat layer 104 and the waterproof layer 108, while the waterproof layer 108 may be disposed between the optical layer 110 and the device layer 106.

FIGS. 2A-2E are schematic cross sectional views of intermediate stages illustrating a method of fabricating a flexible panel 200 in accordance with some embodiments of the invention. The method of fabricating the flexible panel 200 is described as follows. First, as shown in FIG. 2A, a carrier C is provided, a flexible substrate 202 and an overcoat layer 204 are sequentially formed over the carrier C. The carrier C may be a carrier glass or another suitable carrier substrate. The flexible substrate 202 directly contacts the carrier C, and the thickness of the flexible substrate 202 may be less than 20 microns, e.g. about 8 microns to 10 microns. In addition, the flexible substrate 202 may be formed of a transparent material, e.g. polyimide and/or another suitable material. The overcoat layer 204 is formed over the flexible substrate 202; the material of the overcoat layer 204 may include acrylic, diethylene glycol methylethyl ether, methyl 3-methoxypropionate, poly-functional monomers (e.g. ethylene glycol dimethacrylate and/or the material of CAS No. 478556-66-0), additives (e.g. the material of CAS No. 14513-34-9) and/or another suitable organic material, and the thickness of the overcoat layer 204 may be less than 2 microns, e.g. about 0.8 microns to 1.2 microns. According to the material of the flexible substrate 202, the flexible substrate 202 may be formed over the carrier C by coating or another suitable deposition process, or alternatively in a form of layered films, but is not limited thereto. In addition, the overcoat layer 204 may be formed over the carrier C and the flexible substrate 202 by coating or another suitable deposition process. In some embodiments, the overcoat layer 204 may be a structure formed of organic material layers and inorganic material layers that are alternately stacked.

Further, the overcoat layer 204 directly contacts the carrier C at the periphery of the flexible substrate 202. In addition, the peeling force between the overcoat layer 204 and the carrier C is greater than the peeling force between the flexible substrate 202 and the carrier C, and the peeling force between the flexible substrate 202 and the overcoat layer 204 is also greater than the peeling force between the flexible substrate 202 and the carrier C, so as to prevent the flexible substrate 202 from separating from the carrier C. Then, the flexible substrate 202 and the overcoat layer 204 are separated from the carrier C in a subsequent process. The peeling force between the flexible substrate 202 and the carrier C and the peeling force between the overcoat layer 204 and the carrier C may be correspondingly adjusted by respectively adjusting the materials of the flexible substrate 202 and the overcoat layer 204. In some embodiments, the peeling force between the flexible substrate 202 and the carrier C is less than or equal to 20 gf/cm, and/or the peeling force between the overcoat layer 204 and the carrier C is greater than or equal to 100 gf/cm. The overcoat layer 204 has an adhesive force that is greater than 4B after undergoing a cross-cut test according to the ASTM D3359 standard, thereby ensuring the adhesion.

Then, as shown in FIG. 2B, a device layer 206 is formed over the overcoat layer 204. According to the type of the flexible panel 200, the device layer 206 may be a touch electrode layer, a liquid crystal display structure, an organic light emitting diode (OLED) display structure, a micro light emitting diode (micro LED) display structure or another suitable layer or structure. If the device layer 206 is a touch electrode layer, then a sputtering process or a patterning process may be performed to form a sensing electrode including indium tin oxide, indium zinc oxide and/or another suitable material, and then a coating process may be performed to form a protection layer covering the sensing electrode, so as to protect the sensing electrode. The protection layer may be formed of, for example, glass, plastic, acrylic-based resin, siloxane-based resin, polyimide, combinations thereof and/or another suitable material. If the device layer 206 is a display structure, then the device layer 206 can also be bonded to the overcoat layer 204.

Afterwards, as shown in FIG. 2C, a cutting process is performed on the stacked structure of the flexible substrate 202, the overcoat layer 204 and the device layer 206 along a cutting line L. For example, the cutting process may be performed by using a scribing wheel, laser or another suitable method to remove unwanted portions of the flexible substrate 202, the overcoat layer 204 and the device layer 206, and the schematic cross-sectional view after the cutting process is as shown in FIG. 2D. In another embodiment, the device layer 206 may be formed within the area surrounded by the cutting line L, such that, the cutting process is performed only on the stacked structure of the flexible substrate 202 and the overcoat layer 204 but not on the device layer 206.

Then, as shown in FIG. 2E, the stacked structure of the flexible substrate 202, the overcoat layer 204 and the device layer 206 is separated from the carrier C to form the flexible panel 200. The water contact angles of the flexible substrate 202 and the carrier C may be greater than 40 degrees, so as to separate the flexible substrate 202 from the carrier C smoothly.

It can be seen from the above description that, according to the embodiments of the invention, the flexible substrate can be directly formed on the carrier, such that an additional layer that helps release between the carrier and the flexible substrate may not be needed, and the flexible substrate can be separated from the carrier by the overcoat layer thereon, thereby reducing the production costs and ensure the quality of the flexible panel.

Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims. 

What is claimed is:
 1. A flexible display panel, comprising: a flexible display substrate; an overcoat layer disposed over and directly contacting the flexible display substrate, wherein an adhesive force of the overcoat layer obtained according to an ASTM D3359 cross-cut test is greater than 4B; a device layer disposed over the overcoat layer; and an optical layer disposed between the overcoat layer and the device layer.
 2. The flexible display panel of claim 1, wherein the device layer comprises one of a touch electrode layer, a liquid crystal display structure, an organic light emitting diode display structure and a micro light emitting diode display structure.
 3. The flexible display panel of claim 1, wherein a thickness of the overcoat layer is in a range from 0.5 microns to 2 microns.
 4. A method of fabricating a flexible panel, comprising: providing a carrier; forming a flexible substrate over and directly contacting the carrier; forming an overcoat layer over and directly contacting the flexible substrate and the carrier, wherein a peeling force between the overcoat layer and the carrier is greater than a peeling force between the flexible substrate and the carrier; forming a device layer over the overcoat layer; performing a cutting process on a stacked structure of the flexible substrate and the overcoat layer to remove a portion of the overcoat layer that directly contacts the carrier; and separating the device layer, the cut flexible substrate and the cut overcoat layer from the carrier.
 5. The method of claim 4, wherein a peeling force between the overcoat layer and the carrier is greater than or equal to 100 gf/cm.
 6. The method of claim 4, wherein a peeling force between the flexible substrate and the carrier is less than or equal to 20 gf/cm.
 7. The method of claim 4, wherein water contact angles of the flexible substrate and the carrier are all greater than 40 degrees.
 8. The method of claim 4, wherein an adhesive force of the overcoat layer obtained according to an ASTM D3359 cross-cut test is greater than 4B.
 9. The method of claim 4, wherein the overcoat layer includes an organic material layer.
 10. A flexible display panel, comprising: a flexible display substrate; an overcoat layer disposed over and directly contacting the flexible display substrate, wherein an adhesive force of the overcoat layer obtained according to an ASTM D3359 cross-cut test is greater than 4B; a device layer disposed over the overcoat layer; and a waterproof layer disposed between the overcoat layer and the device layer. 